This proposal is designed to investigate the "priming" effect of drugs on drug-seeking behavior. Priming effects may play an important role in relapse among drug abusers: Even a small amount of a drug sampled after a period of abstinence may precipitate a full relapse episode. Studies with laboratory animals and humans suggest that small amounts of preferred drugs (e.g., ethanol, heroin or cocaine) transiently increase the subjective desire for more drugs (in humans) and the likelihood of taking more of the drug. This phenomenon has been neither fully described nor explained. Studies proposed in Series I are designed to describe the phenomenon more fully, by examining whether a small preload dose of ethanol increases subjects' preference for ethanol, relative to money, in a concurrent choice procedure. One experiment will assess the effects of preload dose (0 - 0.8g/kg ethanol) and the other will assess the effect of varying the delay 90 -120 min from preload to choice). Studies proposed in Series II will investigate one process that may interact with the priming effect, that is, the capacity of drugs to impair self-control. Self-control is operationally defined as the tendency to prefer larger, delayed rewards over smaller, more immediate rewards. Drugs of abuse may impair self-control, increasing the likelihood that the individual will choose an immediate reward (e.g., more of the drug) over larger, delayed rewards (e.g., benefits of abstinence). We will assess the direct effects of ethanol, diazepam and d-amphetamine on self-control. Together, these studies will improve our understanding of the priming phenomenon, and suggest behavioral mechanisms which underlie priming effects and relapse.